Double integration using polar coordinates

Ok, got a few small problems. Just gaps in my knowledge I suppose, wonder if anyone can help.

A bit stuck on how to work out the limits for theta. Everything else is fine, it's just that. I know if it says in the first quadrant that it's pi/2 and 0 but thats a really basic one, everything above that, no clue.

Beta function formula for anything that isn't from 0 to pi/2 I don't understand what number you multiply it by. Normal beta function is fine, just that.